protected void StudentRegNoDropDownList_SelectedIndexChanged(object sender, EventArgs e) { EnrollCourse _EnrollCourse = new EnrollCourse(); _EnrollCourse.Id = Convert.ToInt32(StudentRegNoDropDownList.SelectedValue); var StudentData = _EnrollCourseManager.GetStudentData(_EnrollCourse.Id); if (StudentData != null) { txtStudentName.Text = StudentData.StudentName.ToString(); txtStudentEmail.Text = StudentData.StudentEmail.ToString(); } else { ClientScript.RegisterStartupScript(this.GetType(), "alert", "alert('Do Not have Anydata');", true); } }